Composition and Spatial Variation of Germinable Seed Bank in Burned Nothofagus pumilio Forests in Patagonia Argentina

Abstract

The availability of soil-stored seed determines initial plant functional types in post-fire landscapes. We evaluated the post-fire regeneration of Nothofagus pumilio forests, in Patagonia, Argentina, analyzing the soil seed bank (SSB) and the above-ground vegetation (AV). At three sites: La Colisión, Río Turbio and Monte Zeballos, burned in 2008, 1980 and 1941, respectively, we sampled the SSB and AV in two transects from the edge of the remaining forest, up to 90 m within the burned area, and recorded the emergence (198 soil samples) and presence of vascular species. To determine the effect of the distance to the remnant forest on the germinable seed bank, we performed simple linear regression analysis through the use of linear mixed-effect models, and we analyzed the similarity between the composition of SSB and AV with PERMANOVA. The emergence of plant growth forms had different patterns in relation to the distance from the forest in the three sites, which might be associated with the time of fire occurrence, and specific characteristics of each site. The emergence of N. pumilio was registered at more than one distance at the recent burning site. Herbs constituted the main source of cover with 69% of the composition, and native/endemic species represented 71%. This study contributes to the understanding of the relationship between the seed bank and standing vegetation and a better understanding of the resilience of post-fire N. pumilio forests. Our findings suggest that from 15–20 m from the edge, the SSB would be insufficient to ensure the spontaneous recovery of the forest, making active restoration necessary in order to tend to a recovery of the structure and functionality of the original community.

Early vegetation recovery following a mid to high‐severity fire in the Andean‐Patagonian forests

“…Regarding native trees that only regenerate by seeds, the only burned plots where we detected tree regeneration were those with living trees, which probably corresponded to individuals not affected by fire, as it was also found by Landesmann et al (2021). Considering the sensibility and limited dispersion of these species (Cuevas & Arroyo, 1999; Landesmann & Morales, 2018; Urretavizcaya et al, 2022; Urretavizcaya & Defossé, 2004) and the great extent of high severity of the fire, it might take many years or, most probably, the forest ecosystem will not return if tree plantations are not carried out.…”

“…In the early stages after a fire, resprouters usually dominate, and in the mid stages, tree colonization may occur especially close to unburned patches or at low severity, returning to a forest system in the long term (Cavallero et al, 2015). However, as the main trees present a transient seed bank and limited dispersion from unburned areas, forests may be unable to recover if fire severity is moderate to high since the more severe the fire, the greater the loss of litter and duff layers and thus the transient seeds accumulated in the surface soil (Cuevas & Arroyo, 1999;Landesmann et al, 2021;Landesmann & Morales, 2018;Urretavizcaya et al, 2022;Urretavizcaya & Defossé, 2004). In those cases, shrublands establish as alternative states (Rusch et al, 2016(Rusch et al, , 2017.…”

Recuperación temprana de la vegetación tras un incendio de mediana a alta severidad en los bosques andino‐patagónicos

“…En cuanto a los árboles nativos que solo se regeneran por semillas, las únicas parcelas quemadas en las que detectamos regeneración de árboles fueron aquellas con árboles vivos, que probablemente correspondían a individuos no afectados por el fuego, como también fue encontrado por Landesmann et al (2021). Teniendo en cuenta la sensibilidad y limitada dispersión de estas especies (Cuevas & Arroyo, 1999; Landesmann & Morales, 2018; Urretavizcaya et al, 2022; Urretavizcaya & Defossé, 2004) y la gran extensión de la alta severidad del incendio, podría llevar muchos años o, muy probablemente, el ecosistema forestal no retornará si no se realizan plantaciones de árboles.…”

“…En las primeras etapas tras un incendio, suelen dominar las especies rebrotadoras, y en las etapas medias, la colonización por árboles puede ocurrir especialmente cerca de parches no quemados o con baja severidad, volviendo a un sistema forestal en el largo plazo (Cavallero et al, 2015). Sin embargo, dado que las principales especies arbóreas presentan un banco de semillas transitorio y una dispersión limitada desde las zonas no quemadas, los bosques pueden ser incapaces de recuperarse si la severidad del incendio es de moderada a alta, ya que cuanto más severo es el incendio, mayor es la pérdida de hojarasca y capas de mantillo y, por tanto, de las semillas transitorias acumuladas en el suelo superficial (Cuevas & Arroyo, 1999; Landesmann et al, 2021; Landesmann & Morales, 2018; Urretavizcaya et al, 2022; Urretavizcaya & Defossé, 2004). En esos casos, los matorrales se establecen como estados alternativos (Rusch et al, 2016, 2017).…”

Genomic responses to climate: Understanding local adaptation in the Andean tree species Nothofagus pumilio and implications for a changing world

“…Linear distance among paired sites within a locality was always less than three kilometers, to stay within reasonable gene flow distance. Gene flow information is limited for Nothofagus species, but estimates from related species and natural post‐fire regeneration suggest pollen and seed dispersal may be limited to 45–60 m from adult trees (Sola et al, 2020; Urretavizcaya et al, 2022). The elevation difference among the paired sites' centroids was at least 150 m to capture an approximate 1–2°C difference in mean annual temperature due to lapse rate (Whiteman, 2000).…”